An enhanced electron transport chain improved astaxanthin production in
Phaffia rhodozyma
Abstract
Astaxanthin (AX) is a carotenoid pigment with antioxidant properties. AX
is used widely in the animal feed industry as a supplement. Wild-type
strains of Phaffia rhodozyma naturally produce low AX yields, but we
increased AX yields 50-fold in previous research using random
mutagenesis of P. rhodozyma CBS6938 and fermentation optimisation.
Genome sequencing linked phenotype and genome changes of the increased
AX production but relevant metabolic changes were not resolved. In this
study, the wild-type and the superior P. rhodozyma mutant strains were
grown in chemically defined media and instrumented fermenters.
Differential kinetic, metabolomics, and transcriptomics data were
collected. Our results suggest that carotenoid production was mainly
associated with cell growth and had a positive regulation of central
carbon metabolism metabolites associated with glycolysis, the pentose
phosphate pathway, the TCA cycle, and amino acids and fatty acids
biosynthesis. In the stationary phase, amino acids associated with the
TCA cycle increased, but most of the fatty acids and central carbon
metabolism metabolites decreased. TCA cycle metabolites such as
succinate, fumarate, and α-ketoglutarate were in abundance during both
growth and stationary phases. The overall observed metabolic changes in
the central carbon metabolism and abundance of TCA cycle metabolites
suggest an improvement in the electron transport chain and the provision
of the electrons required for the AX synthesis. Transcriptomic data
correlated with the metabolic data and found a positive regulation of
genes associated with the electron respiratory chain suggesting this to
be the main driver for improved AX production in the mutant strain.